B&Q's bedding plants, grown by Coletta & Tyson and Roundstone, are already neonicotinoid-free.
B&Q launched a Nature of Gardens report this week to give ideas how to make gardens more wildlife friendly and give evidence why that is a good idea.
Head of horticulture Tim Clapp said: "Neonicotinoids are fundamentally not good so we have worked in conjunction with our growers to come up with a plan. We weren't large users anyway and now we have made a strong statement we won't use neonicotinoids at all. It's really important we show leadership on sustainability."
B&Q sustainabilty manager Rachel Bradley said: "To further support pollinators, we are encouraging everyone to do more for wildlife and to that end we will ensure that none of the flowering plants we sell will be grown using any pesticide containing any of the nine neonicotinoids."
He said the issue was on hardy nursery stock rather than bedding and that growers were using biocontrols rather than neonicotinoids to control vine weevil now.
B&Q sells more than one million lavenders a year.
In the US, Lowe's and Home Depot have phased out neonicotinoids after pressure group campaigns and in the UK similar campaigns from 38 Degrees began in 2016.
Consumer products containing clothianidin, thiamethoxam and imidacloprid were banned by the EU in 2013.
Meanwhile, the latest NFU application for an emergency authorisation for neonicotinoid seed treatments has been declined by Defra minister George Eustice.